In order to evaluate drought resistance in barely genotype and for screening drought tolerance indices, 26 genotypes of barley were tested in a randomized complete block design with three replications under normal and water stress conditions in the faculty of Agriculture, University of Tehran. Based on the yield potential (Yp) and yield stability (Ys), som quantitative criteria of drought resistance such as: mean productivity (MP), tolerance index(TOL), geometric mean productivity(GMP), harmonic mean(HM), stress susceptibility index(SSI) and stress tolerance index(STI) were figured out. High significant differences were observed among genotypes for all indices and for potential and stress yields, indicating the existence of genetic variation and possibility of selection for drought resistance as well as possibility of hybridization for the genetic and breeding studies. The highest potential and stress yield, MP, GMP, and STI belonged to Genotypes Radical, Badia and Sina. Correlation analysis among indices, potential and stress yield indicated that the most suitable criteria for screening barley genotypes were MP, GMP, and STI. Regarding these criteria and high Yp and Ys, the most drought tolerance genotypes were identified as Kavir, Badia, Radical, Terean78 and Sina. Multivariate biplot indicated that genotypes Badia, Kavir, Radical, Terean78 and Sina were located close to the vectors of such drought tolerance indices, as: MP, GMP and STI. Distribution of the genotypes in the biplot space indicated the presence of genetic diversity among the genotypes for drought stress.Cluster analysis placed genotypes in three groups as based on information of either of the two conditions, with tolerant genotypes being placed in different clusters.
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